Prism: A file server architecture for providing integrated services.

摘要

Multimedia data may be represented in various forms—text, data, image, audio, video, etc. In an integrated multimedia server, request streams accessing these various types of data stored in the server share server resources such as CPU resources, I/O bandwidth, network bandwidth, disk space, and memory space. In this thesis we identify three different service classes: periodic, aperiodic and interactive, based on the characteristics of the service required by data streams belonging to each service class. Service required by any access stream of the storage server falls into any one of the three classes. Prism is a multimedia storage system architecture for providing these three services by multiplexing limited disk I/O bandwidth among competing access streams.; Prism separates resource allocation and resource scheduling into different system-level entities. Resource allocation is done through a system level administrative policy, and scheduling is done at the resource level (at the disk device or network interface). Resource allocation is enforced through an admission control library. Resource scheduling is done within layered drivers residing just above the device drivers in the operating system stack. Prism's architecture is flexible enough to support network-attached disk drives and multi-homed devices.; We present a novel admission control algorithm for periodic streams and a novel disk I/O scheduling algorithm for an integrated storage server. We present Prism architecture designed to accommodate the scheduler and the admission controller. Prism architecture includes an I/O library, a QOS context manager, and a layered driver architecture. We also present the application level support required at the server front end of a Prism server. Server side front-end support includes an admission controller and server-push architecture simulation for periodic streams. We have implemented Prism on the Linux operating system. We have also modified the Linux NFS server implementation to accommodate Prism. We present these implementation details and compare Prism's performance with standard Linux and show that Prism achieves the objectives of an integrated storage server.